The Siberian rivers discharge huge amounts of freshwater and terrestrial material into the Arctic Ocean. The elemental compositions and stable carbon isotope values of organic matter in combination with the terrestrial tracer lignin are presented for 12 Siberian rivers. Along 4000 km of coastline, particulate and dissolved organic matter (POM and DOM) were investigated in detail. POM transported by rivers, which drain Taiga regions, originated from C3 plant material consisting of gymnospermous wood with portions of non-woody tissues. POM from the Tundra also stemmed from C3 plants as shown by its stable carbon composition. Compared to the Taiga material a higher contribution of non-woody and angiosperm tissues was found. The carbon / nitrogen ratio showed values typical for soil. The contribution of C4 plants as well as phytoplankton and zooplankton to the particulate material was negligible. The lignin composition of the DOM was related to that of POM but showed a higher degree of degradation being supported by high C/N ratios. The signature of the riverine organic material changed dramatically when entering the Arctic Ocean.